should be a slide out plastic drawer like bit at bottom of boiler with a plastic t shaped key on it. the key slots into a hole on the underside of boiler and twist to lock in place, then turn the nut/screw next to it to fill with water (about 1.2bar if system cold/ 1.5bar if alreafy hot) remember to turn off again. do a google image search of worcester (manufacturer) filling loop and u should get a pic of key and bit u plug it into (black bit on pic but may be white/grey)
billy
December 2010